Antisporulant action of fungicides against Podosphaera leucotricha on apple seedlings

A number of commercial fungicides and dinitrophenolic compounds were tested for their ability to suppress further sporulation of established infections of the apple mildew fungus Podosphaera leucotricha on seedlings in the greenhouse. Although they did not kill the fungus, two organophosphorus and two benzimidazole‐type compounds gave powerful suppression for at least 18 days. Other fungicides known to control apple mildew in the field had a less marked effect. Sporulation occurred on subsequent untreated growth to the same extent as on control seedlings, except where either of two substituted dinitrophenols had been used.